Ambidextrous ungulates have more flexible behaviour, bolder personalities and migrate less

The effects of challenge or social buffering on cortisol, testosterone, and antler growth in captive red deer (Cervus elaphus) males

We equipped 17 captive red deer males (Cervus elaphus) with GPS collars to measure inter-individual distances throughout the 5-months of the antler growth period. We expected some individuals to associate regularly with others while others would not. We predicted that males aggregating with others within a socially stable environment (Associates) would benefit from a form of "social buffering" and would likely have lowered cortisol (C) and testosterone (T) concentrations. Males only irregularly joining social groupings would experience elevated levels of aggression; according to the "Challenge hypothesis", their T and C concentrations should increase. Interacting with a higher proportion of Associates did indeed reduce C concentrations. Conversely, avoiding Associates and challenging other males stimulated the T secretion. Admittedly, males avoiding regular proximity to others tended to develop the largest antlers. They probably benefited from frequent successful agonistic threats to conspecifics, resulting in elevated T concentrations. Regular association with tolerant, conspecifics and "social buffering" did not seem sufficient for producing larger antlers despite reducing C concentrations. Alternative social strategies were adopted within the same group of individuals and showed how the trade-off between these strategies could have an essential impact on C and T concentrations.

Is There an Association between Paw Preference and Emotionality in Pet Dogs?

Research with humans and other animals has suggested that preferential limb use is linked to emotionality. A better understanding of this still under-explored area has the potential to establish limb preference as a marker of emotional vulnerability and risk for affective disorders. This study explored the potential relationship between paw preference and emotionality in pet dogs. We examined which paw the dogs preferentially used to hold a Kong™ and to perform two different locomotion tests. Dogs’ emotionality was assessed using a validated psychometric test (the Positive and Negative Activation Scale—PANAS). Significant positive correlations were found for dogs’ paw use between the different locomotion tasks, suggesting that dogs may show a more general paw preference that is stable across different types of locomotion. In comparison, the correlations between the Kong™ Test and locomotion tests were only partially significant, likely due to potential limitations of the Kong™ Test and/or test-specific biomechanical requirements. No significant correlations were identified between paw preference tests and PANAS scores. These results are in contrast to previous reports of an association between dog paw preference and emotionality; animal limb preference might be task-specific and have variable task-consistency, which raises methodological questions about the use of paw preference as a marker for emotional functioning.

Paw preferences in mice and rats: Meta-analysis

Mice and rats are among the most common animal model species in both basic and clinical neuroscience. Despite their ubiquity as model species, many clinically relevant brain-behaviour relationships in rodents are not well understood. In particular, data on hemispheric asymmetries, an important organizational principle in the vertebrate brain, are conflicting as existing studies are often statistically underpowered due to small sample sizes. Paw preference is one of the most frequently investigated forms of hemispheric asymmetries on the behavioural level. Here, we used meta-analysis to statistically integrate findings on paw preferences in rats and mice. For both species, results indicate significant hemispheric asymmetries on the individual level. In mice, 81 % of animals showed a preference for either the left or the right paw, while 84 % of rats showed this preference. However, contrary to what has been reported in humans, population level asymmetries were not observed. These results are particularly significant as they point out that paying attention to potential individual hemispheric differences is important in both basic and clinical neuroscience.

No evidence that footedness in pheasants influences cognitive performance in tasks assessing colour discrimination and spatial ability

The differential specialization of each side of the brain facilitates the parallel processing of information and has been documented in a wide range of animals. Animals that are more lateralized as indicated by consistent preferential limb use are commonly reported to exhibit superior cognitive ability as well as other behavioural advantages. We assayed the lateralization of 135 young pheasants (Phasianus colchicus), indicated by their footedness in a spontaneous stepping task, and related this measure to individual performance in either 3 assays of visual or spatial learning and memory. We found no evidence that pronounced footedness enhances cognitive ability in any of the tasks. We also found no evidence that an intermediate footedness relates to better cognitive performance. This lack of relationship is surprising because previous work revealed that pheasants have a slight population bias towards right footedness, and when released into the wild, individuals with higher degrees of footedness were more likely to die. One explanation for why extreme lateralization is constrained was that it led to poorer cognitive performance, or that optimal cognitive performance was associated with some intermediate level of lateralization. This stabilizing selection could explain the pattern of moderate lateralization that is seen in most non-human species that have been studied. However, we found no evidence in this study to support this explanation.

Learning is negatively associated with strength of left/right paw preference in wild grey squirrels (Sciurus carolinensis)

Cerebral laterality, via hemispheric specialisation, has been evidenced across the animal kingdom and linked to cognitive performance in a number of species. Previously it has been suggested that cognitive processing is more efficient in brains with stronger hemispheric differences in processing, which may be the key fitness benefit driving the evolution of laterality. However, evidence supporting a positive association between cognitive performance and lateralization is mixed: data from studies of fish and birds show a positive relationship whereas more limited data from studies of mammals suggest a weak or even negative relationship, suggesting the intriguing possibility of a mammal/non-mammal divide in the nature of this relationship. Here, we report an empirical test examining the relationship between lateralization and cognitive performance in wild grey squirrels (Sciurus carolinensis) by measuring left/right paw preference as a behavioural assay of cerebral lateralization and learning speed as an assay of cognitive efficiency. We carried out a motor-based laterality test using a reaching paradigm and measured learning speed on a problem-solving task. In accordance with the suggestion of a mammal/non-mammal divide, we found a negative relationship between strength of paw preference and performance on the learning task. We discuss this finding in light of niche-specific adaptations, task-specific demands and cognitive flexibility.

Animal learning may contribute to both problems and solutions for wildlife-train collisions

Transportation infrastructure can cause an ecological trap if it attracts wildlife for foraging and travel opportunities, while increasing the risk of mortality from collisions. This situation occurs for a vulnerable population of grizzly bears (Ursus arctos) in Banff National Park, Canada, where train strikes have become a leading cause of mortality. We explored this problem with analyses of rail-associated food attractants, habitat use of GPS-collared bears and patterns of past mortality. Bears appeared to be attracted to grain spilled from rail cars, enhanced growth of adjacent vegetation and train-killed ungulates with rail use that increased in spring and autumn, and in areas where trains slowed, topography was rugged, and human density was low. However, areas with higher grain deposits or greater use by bears did not predict sites of past mortality. The onset of reported train strikes occurred amid several other interacting changes in this landscape, including the cessation of lethal bear management, changes in the distribution and abundance of ungulates, increasing human use and new anthropogenic features. We posit that rapid learning by bears is critical to their persistence in this landscape and that this capacity might be enhanced to prevent train strikes in future with simple warning devices, such as the one we invented, that signal approaching trains. This article is part of the theme issue 'Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation'.

Individual-Level and Population-Level Lateralization: Two Sides of the Same Coin

Lateralization, i.e., the different functional roles played by the left and right sides of the brain, is expressed in two main ways: (1) in single individuals, regardless of a common direction (bias) in the population (aka individual-level lateralization); or (2) in single individuals and in the same direction in most of them, so that the population is biased (aka population-level lateralization). Indeed, lateralization often occurs at the population-level, with 60–90% of individuals showing the same direction (right or left) of bias, depending on species and tasks. It is usually maintained that lateralization can increase the brain’s efficiency. However, this may explain individual-level lateralization, but not population-level lateralization, for individual brain efficiency is unrelated to the direction of the asymmetry in other individuals. From a theoretical point of view, a possible explanation for population-level lateralization is that it may reflect an evolutionarily stable strategy (ESS) that can develop when individually asymmetrical organisms are under specific selective pressures to coordinate their behavior with that of other asymmetrical organisms. This prediction has been sometimes misunderstood as it is equated with the idea that population-level lateralization should only be present in social species. However, population-level asymmetries have been observed in aggressive and mating displays in so-called “solitary” insects, suggesting that engagement in specific inter-individual interactions rather than “sociality” per se may promote population-level lateralization. Here, we clarify that the nature of inter-individuals interaction can generate evolutionarily stable strategies of lateralization at the individual- or population-level, depending on ecological contexts, showing that individual-level and population-level lateralization should be considered as two aspects of the same continuum.

Migratory plasticity is not ubiquitous among large herbivores

The migratory movements of wild animals can promote abundance and support ecosystem functioning. For large herbivores, mounting evidence suggests that migratory behaviour is an individually variable trait, where individuals can easily switch between migrant and resident tactics. The degree of migratory plasticity, including whether and where to migrate, has important implications for the ecology and conservation of large herbivores in a changing world. Mule deer (Odocoileus hemionus) are an iconic species of western North America, but are notably absent from the body of literature that suggests large herbivore migrations are highly plastic. We evaluated plasticity of migration in female mule deer using longitudinal GPS data collected from 312 individuals across nine populations in the western United States, including 882 animal-years (801 migrants and 81 residents). We followed both resident and migratory mule deer through time to determine whether individual animals switched migratory behaviours (i.e., whether to migrate) from migratory to residency or vice versa. Additionally, we examined the fidelity of individuals to their migration routes (i.e., where to migrate) to determine whether they used the same routes year after year. We also evaluated whether age and reproductive status affected propensity to migrate or fidelity to migratory routes. Our results indicate that mule deer, unlike other large herbivores, have little or no plasticity in terms of whether or where they migrate. Resident deer remained residents, and migrant deer remained migrants, regardless of age, reproductive status or number of years monitored. Further, migratory individuals showed strong fidelity (>80%) to their migration routes year after year. Our study clearly shows that migration plasticity is not ubiquitous among large herbivores. Because of their rigid migratory behaviour, mule deer may not adapt to changing environmental conditions as readily as large herbivores with more plastic migratory behaviour (e.g., elk). The fixed migratory behaviours of mule deer make clear that conservation efforts aimed at traditional seasonal ranges and migration routes are warranted for sustaining this iconic species that continues to decline across its range.

Assessing animal individuality: links between personality and laterality in pigs

Animal individuality is challenging to explain because individual differences are regulated by multiple selective forces that lead to unique combinations of characteristics. For instance, the study of personality, a core aspect of individuality, may benefit from integrating other factors underlying individual differences, such as lateralized cerebral processing. Indeed, the approach-withdrawal hypothesis (the left hemisphere controls approach behavior, the right hemisphere controls withdrawal behavior), may account for differences in boldness or exploration between left and right hemispheric dominant individuals. To analyze the relationships between personality and laterality we tested 80 male piglets with established laterality patterns for 2 motor functions (tail curling direction and the side of the snout used for manipulation) and a combined classification integrating both motor functions using cluster analysis. We analyzed basal salivary testosterone and cortisol along with their behavior in standardized tests as pre-established indicators of different personality traits (Boldness, Exploration, Activity, Sociability, and Coping). We found that the direction of the single motor biases showed significant associations with few personality traits. However, the combined laterality classification showed more, and more robust, significant associations with different personality traits compared with the single motor biases. These results supported the approach-withdrawal hypothesis because right-biased pigs were bolder and more explorative in a context of novelty. Additionally, right-biased pigs were more sociable than left-biased pigs. Therefore, the present study indicates that personality is indeed related to lateralized cerebral processing and provides insight into the multifactorial nature of individuality.

Intermediate frequency of aversive conditioning best restores wariness in habituated elk (Cervus canadensis)

In protected areas around the world, wildlife habituate to humans and human infrastructure, potentially resulting in human-wildlife conflict, and leading to trophic disruptions through excess herbivory and disconnection of predators from prey. For large species that threaten human safety, wildlife managers sometimes attempt to reverse habituation with aversive conditioning. This technique associates people as a conditioned stimulus with a negative, unconditioned stimulus, such as pain or fright, to increase wariness and prevent the need for lethal wildlife management. Resistance to aversive conditioning by some habituated individuals often results in more frequent conditioning events by managers, but there are few studies of conditioning frequency with which to evaluate the usefulness of this management response. We evaluated the effect of conditioning frequency on the wariness of elk (Cervus canadensis) by subjecting marked individuals to predator-resembling chases by people over a period of three months. In that time, animals were subjected to conditioning a total of 3, 4, 5, 6, 7, or 9 times which we analyzed as both an ordinal variable and a binary one divided into low (3-5) and high (6-9) conditioning frequencies. We measured wariness before, during, and after the conditioning period using flight response distances from an approaching researcher. During the conditioning period, overall wariness increased significantly for elk in both treatment groups, although the increase was significantly greater in individuals subjected to high conditioning frequencies. However in the post-conditioning period, wariness gains also declined most in the high-frequency group, equating to more rapid extinction of learned behaviour. Across all treatment frequencies, rapid changes in flight responses also characterized the individuals with the lowest wariness at the beginning of the study period, suggesting that individuals with greater behavioural flexibility are more likely to habituate to both people and their attempts to change wariness via aversive conditioning. Together, our results imply that aversive conditioning may be most effective at intermediate frequencies and that its utility might be further increased with proactive assessment of individual personalities in habituated wildlife.